The present invention relates to a scroll type compressor which compresses introduced fluid by moving fluid pockets formed between a fixed scroll and a movable scroll while changing their volumes.
In general, a scroll type compressor includes a fixed scroll and a movable scroll which form fluid pockets therebetween to introduce a fluid such as a refrigerant therein. The scroll type compressor further includes a driving mechanism connected to the movable scroll and a main shaft which is connected an electromagnetic clutch unit known in the art. When the main shaft is rotated with the electromagnetic clutch unit being set on, the driving mechanism causes a circular orbital motion of the movable scroll in the manner known in the art. The orbital motion of the movable scroll causes the fluid pockets to move and change their volumes to thereby compress the fluid.
At a moment when started, the scroll type compressor has a starting torque upon operation of the electromagnetic clutch. In a case where the scroll type compressor is installed in an automobile, the starting torque gives a discomfortable shock to a driver. This is because the starting torque is relatively large.
In view of this disadvantage, there has been available a compressor with a soft start mechanism, wherein a soft start can be carried out to reduce the starting torque using the soft start mechanism. An example of the compressor with the soft start mechanism is described in detail in Japanese Second (examined) Patent Publication No. 1-52592 and will later be discussed in conjunction with the drawing.
In the conventional compressor, however, the condition for carrying out the soft start is limited with respect to the compressor speed and the ambient temperature. When the operating pressure is set high, there is a problem that, when the compressor speed is low or the ambient temperature is low, the pressure in a discharge chamber increases so slowly that the take-in volume can not be obtained sufficiently. On the other hand, when the operating pressure is set low, there is a problem that when the compressor speed is high or the ambient temperature is high, the pressure in the discharge chamber increases so quickly that the take-in volume becomes sufficient at once and thus the soft start effect can not be expected.